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Polarity: Polar or Non-Polar Covalent –That is the Question?
Does the molecule have polar covalent bonds?
Yes
No
Is the Lewis structure symmetrical?
Non-polar Covalent
Yes
Non-polar
Covalent
No
Polar
Covalent
Polarity:
Polarity results from the uneven partial charge distribution between various atoms in a
compound. Atoms, such as nitrogen, oxygen, and halogens, that are more electronegative have a
tendency to have partial negative charges δ-. Atoms, such as carbon and hydrogen, have a tendency to
be more neutral or have partial positive charges δ+.
Dipole:
Electrons in a polar covalent bond are unequally shared
between the two bonded atoms, which results in partial positive and
negative charges. The separation of the partial charges creates a
dipole. The word dipole means two poles: the separated partial
positive and negative charges. The dipole is draw with the tail and
cross towards the positive atom, and the arrow head is pointing
towards the negative atom.
Polar vs. Non-polar Covalent:
Non-polar molecules are of two types. Molecules whose atoms have equal or nearly equal
electronegativities have zero or very small dipole moments. These molecules are symmetrical. A second
type of non-polar molecule has polar bonds, but the molecular geometry is symmetrical allowing the
bond dipoles to cancel each other.
Ex: Carbon dioxide and “HOFBrINCl” the clown!
Polar molecules results when a molecule contains polar bonds in an unsymmetrical arrangement.
Ex: Water and ammonia NH3